In my prior U.S. Pat. No. 3,595,362, issued on July 27, 1971, there was shown and claimed a typewriter of the single-element (golf ball) type which was provided with error-correcting mechanism having a correction key associated with the keyboard, operating to control a correcting ribbon in turn associated with a marking ribbon. In several of my prior U.S. and foreign patents cited in that U.S. Pat. No. 3,595,362 or referred to therein, for example U.S. Pat. Nos. 3,114,447; 3,141,539; 3,149,711; 3,154,183 and 3,204,745, there had been shown and described various arrangements by which corrections could be accomplished in typewriters of the more common plural-element types, e.g. of the type-basket construction.
The principal commercial source of single-element typewriters has been the International Business Machines Corporation (IBM), who have marketed many thousands of such typewriters under the registered Trademark "Selectric". It is considered likely that such machines will continue in commercial use, either as new or rebuilt typewriters, or as used type-writers, for many years to come. Moreover, there has quite recently come onto the market an improved form of single-element typewriter which incorporates special features for the making of corrections; this typewriter is known by the trademark name Correcting "Selectric" Typewriter. The special features employed in this new typewriter are not themselves adaptable to the older Selectric typewriters, and it would therefore be very desirable if there were some way in which the owners of the older style single-element machines could obtain, at moderate cost, the advantages of modern error-correction operation; that is, without the cumbersome and inefficient purely manual use of error-correcting materials.
In U.S. Pat. No. 3,724,633, issued Apr. 3, 1973, to the above-mentioned company, some features of the Correcting Selectric Typewriter have been described, and also the main characteristics and differences between correction materials employed in so-called camouflage or cover-up error correction procedures, and so-called "lift-off" procedures. That U.S. Pat. No. 3,724,633 therefore, constitutes useful background information for an understanding of my present invention, whose main object is to provide owners of now conventional single-element typewriters with efficient yet relatively inexpensive error-correction facilities, easy of application to existing typewriters, and with optional degrees of automation, or what is perhaps better called "automaticity".
In summary, this invention provides add-on units or auxiliary elements or clip-on accessories, applicable in very simple ways to existing golf-ball single-element typewriters, without the need for tools or skilled mechanics, whereby provisions for error-correction may be provided at very low cost.
The auxiliaries clip onto the existing mechanism plates from above, without interfering with the usual ribbon cartridges.
The invention also contemplates that the operator will not have to raise the cover panel of the typewriter in order to control the ribbon, and can readily make corrections without having direct access to the existing ribbon controls, such as the vibrator throw control.
The auxiliary frame of the invention is applied on top of the existing mechanism plate of the machine (the ribbon cartridge being first removed), in space which is available between the existing plate and the cartridge; the ribbon cartridge is then replaced between the usual clips and guides provided for that purpose.